Optical products



May 21, 1957 c. D. WEST OPTICAL PRODUCTS mea March 17, 1953 diai'io FIG.

FIG. 2

- INVENTOR.

' ATTORNEYS United States Patent OPTICAL PRODUCTS Cutler D. West, Cambridge, Mass., assignor to Polaroid Corporation, Cambridge, Mass., a corporation of Delaware Application March 17, 1953, Serial No. 342,812

3 Claims. (Cl. 154-2.65)

This invention relates to optical products in which optical surfaces are joined by a cement and to processes of their manufacture.

Objects of the invent-ion are: to provide a variety of optical products in which optical surfaces are joined by a. cement containing succinonitrile as its characteristic ingredient; and to provide processes of manufacturing optical products of the foregoing type.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises several steps and the relation and order of one or more of such steps with respect to each of the others, and the product possessing the features, properties and the relation of elements which are exemplified in the following detailed disclosure, and the scope of the application of which will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawing wherein:

Figure 1 is a schematic cross-sectional view of an achromatic doublet embodying the invention; and

Fig. 2 is a schematic cross-sectional view of an electrooptical light valve embodying the present invention.

Patented May 21, 1957 least two optical surfaces that are joined by a cement which, because it contains succinonitrile as its characteristic or predominant ingredient, possesses the following physical, chemical and optical properties: optical clarity; refractive index (N '=1.45) of the same order of magnitude as that of optically useful gla: and plastics; isotropy within the temperature range of from 40 to 57.2 C; low volatility; strong cohesive forces; strong adhesive forces relative to optically useful glass and plastic materials; and chemical stability. The unique properties of succinonitrile are believed to be the consequence of its rare molecular structure characterized by a molecule which is small in size, which possesses a plurality of strong dipoles in motion with respect to each other, and which is rotatable about its center.

Specifically, the aforementioned cement is composed of one of the following: (1) substantially pure succinonitrile; (2) commercial succinonitrile (containing a small quantity of water); and (3) a mixture containing from to 99-plus percent by total weight of succinonitrile and from a trace to 5 percent of at least one other material upon which the properties of the mixture (i. e., temperature range of stability, refractive index, dielectric constant, etc.) partially depend.

The following is a list of the properties of pure and commercial succinonitrile:

The following is a list of the properties of other compounds with at least one of which succinonitrile may be Products embodying the present invention provide at 40 advantageously mixed.

TABLE II Melt- Boll- Molectng lng ular Density Molar Point, Point, Weight Volume- Dlcyan acetylene 21 76. 5 76. 05 0. 970 78. 4-

NOC=OON Succinlc acid 185 235 118. 0b 1. 664 75. 5 HOOCOHsOBaOOOH Ethylene chloride -a5 as as. as 1. 2151 78. 8

Ethylene bromide 10 182 187. 86 2. 86. 5

BrOHIOIhBr Methylene iodide 6 207. B6 3. 325 80. 5

Methyl glycolate 1B1 90. 05 l. 168 77. 2 OH;OHOOOOH:

Glycerol 18 290 92. 06 1.200 73.0 OHIOHOHOHOHIOH Trlmethylene glycol 214 76. 06 1. 053 72. 2

HO(CH|)|OH Propylene glycol 189 76. 06 1.040 73. 1 CHsOH OH OH 0H1 Ethylene glycol monomethyl other 124 76.06 0. 966 79. 4

OHIOOHIOHIOH 4 Proplonlc acid 141 74. 06 0. 902 75. 0 QHiOHsOOOH manna II.-Con'tinued Melting Bolling Molecular Molar Point, Point, Weight Density Volume so. i 90.

Proplonltrlle mi, .sspti 0.788 10.4 oniousoN n-Bntyronitrile :ats' looms; one see CHKGHMON Butyrolactone 20s 86:05 1.129 was l:t-(UH1)ICQ: I I

lvi'idloxane I 1.035 88:1 :(oHnrowHm: '(dlpnle'h'eeh I Benzene. 5; -s at mi (1884 88.3 'CiHs (dipole tree) The value for a -givenproperty-oi s. mixture :of :succinonitrile and one of the-foregoing:compoundslies'between the value for that property of succinonitrile nndlho'valuo for that property of the compound with :which the'succinonitrile is ,mixed. t

Two methods of fabricating products tembod'yingrtho present invention are preferred. .Thc'iirst, azcasting process, comprises the-steps of-predeterminedly positioning a pair of optical surfaces with respectto .each-othen-poun ing between them a liquid cement of the foregoing type, and permitting the liquid ccment'to freeze. The second, an extruding process, comprises the'steps of locating-between a pair of optical surfaces a solid cement of the foregoing typcandpressing the surfaces toward each other into predetermined relative positions.

With referencenow tothe-drawing, Fig. lshows-an achromatic doublet I0 embodying the invention. Achromatic doublet comprises a pair of thin lenscs'll and 12, the adjacent optical surfaces of which are contiguous. Lens 11 is composed of a first, optically useful material such-.asflint glass and.'lensrJ2 is:composedof-ta second, optically useful material'such iasucrown glass. Joining the adjacent surfaces of the lens islnr thin'dayer'rnrof .a cement which contains succinonitn'le As its characteristic ingredient. An edge seal 14 composed of a suitable metal is provided to prevent the cement in layer 13'from evaporating.

it is well'known that of thentotal light flux incident upon the interface between two'diffcrent materials, the percentage reflected rather than refracted is a'directfunction of the difference between the indlces of refraction of the two materials. Although the difierence between the indiccs of refraction of lenses of !the type ordinarily used in an achromatic .doublet is not significantrin this' respect, the differences betweemthe indices of refraction of the thin layer of air between the adjacent surfaces of these lenses and the lenses themselves ordinarily is a reciable. Such a layer of air, therefore, often'is responsibic for the reflection oftan appreciable proportion of incident/light. in the case .of achromatic doublets", however, since the index of refraction of layer 13 isiof thesame ordertof magnitude as the indices of refraction of lenses 11 and 12, layer 13; in addition to ioiningt'the lcnscs, substantially eliminatesJeflection at the joined surfaces.

Theembodimcnt ofithe present invention shown'in Fig. 2 is-anelcctrooptical light:valve,--generally designated by 15,-which comprises a pair of crossed polarizing elcfashion, when subjected to an electrostatic flold,iintroduces a phase difference between linear components .Of incident polarized light. Light valve't15 specificallyicomprises, in continuous sequence, a first;po1arizing'iilt'er 16, a layer 17 of cement, a transparent-electrical conductor meals and therebetwccn aecrystal which, in conventional -"-U- 18, azlayer 19 of cement, .a crystal .20 :which, .wl1en.subjected ,to tan electrostatic -field, introduces a phase ditierence between linear components of incident polarized light, a-layerjtofcement, aatransparent electrical conductor 22, a layer 23 of cement and aisecondpolarizing filtor.24 crossed with;respectto .firs ttpolarizing filter-.16. In one form, light valve 15 comprises a crystal composed .of rcuproushalide, transparentelectrical conductors 18 tends: composed-mfglasshaving Nesa: coatings which aretadiacent -.to.crystalt 20, layers .17, .19, 21 and-23. composed: Otto-cement whichcontains succinonitrile-tas its characteristicfingredient, andpolarizingifilters 16. and .24 ofiamnvcntionaltypc.

In operation, assuming that polarizing filtersilfiaand 24;: are .:linear,.in: the sabsence -of.ran:-.electrostatic field-tapplied'rtomrystal. 20,';light tvalvev15 acts ass a; closed-shutter tortincidenti light. However, \whenanrelectnostatic stere is applied to crystal 20, a phase: difiencncerbetween linear components of :lig'httransmitted zbymolarizing filter 16 is introduced so that at least .a proportion .of'thislight can pass-sthroughnpolariningfilter J4: ltiiszapparent that: the proportion of tincident'tlight transmitted day.- light' -valve- 15 is=dependont nan-the intensity of :thetelcctrostatic'rfield applied to the crystal 20 and that this electrostatic field may be varied in order to vary the proportion of light transmitted. Here, layers 17, 19, 21 and 23 substantially eliminate reflection at the surfaces which they join. Furthermore, layers 19 and 21 are desirable, from an electrical standpoint, in that, because they possess a lower' conductivity than does crystal 20, they do not appreciably disrupt an electrical field to which the crystal is being subjected.

It is to be understood that lenses of various shapes can be joined by cements embodying the present invention. 'Where the joined surfaces have difierent curvatures, the cement acts both as an adhesive and as a plastic lens.

Since certain changes may be made in the above prodnet and process without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

-dominant ingredient, and a third layer composed of glass.

2. A laminated product comprising, in sequence, a first layer composed of glass, a second layer composed of an Adhesive material containing at least about succinonitrile, and a third layer composed of glass.

3. A laminated product comprising, in sequence, a first layer composed of glass, a second layer composed of an adhesive material containing succinonitrile as its pre- References Cited in the file of this patent UNITED STATES PATENTS Wainer Dec. 8, 1942 8 Penberthy Aug. 14, 1945 Carpenter Jan. 13, 1948 Kropa Nov. 9, 1948 Land Jan. 3, 1950 Nadeau et a1. Jan. 10, 1950 Marks Mar. 6. 1951 Mason Aug. 1'6, 1953 

1. A LAMINATED PRODUCT COMPRISING, IN SEQUENCE, A FIRST LAYER COMPOSED OF GLASS, A SECOND LAYER COMPOSED OF AN ADHESIVE MATERIAL CONTAINING SUCCINONITRILE AS ITS PREDOMINANT INGREDIENT, AND A THIRD LAYER COMPOSED OF GLASS. 